1. Field of the Invention
The present invention generally relates to reproducing apparatus and more particularly to a reproducing apparatus for use with, for example, a so-called 8-mm video tape recorder (8-mm VTR) or the like.
2. Description of the Prior Art
Conventional video tape recorders, such as an 8-mm video tape recorder and so on are designed so as to process either a monaural audio signal in which a carrier of an audio signal is 1.5 MHz or a stereo audio signal in which a carrier of one audio signal is 1.5 MHz and a carrier of the other audio signal is 1.7 MHz. In the 8-mm video tape recorder which records and/or reproduces the stereo audio signal, if an audio signal in the signal to be recorded is a stereo signal, then such audio signal is not processed and directly recorded on a magnetic tape. If the audio signal in the signal is a bilingual signal (e.g., Japanese, English, etc.), then the vertical blanking period, for example, of the audio signal is boosted by about 7 dB above the normal level and then recorded on the magnetic tape. A recording format for recording a television signal is represented in FIG. 1, wherein a left audio signal (hereinafter simply referred to as an AFM (audio FM) signal) utilizes a carrier of 1.5 MHz and a right audio signal (AFM signal) utilizes a carrier of 1.7 MHz. These left and right audio signals are FM-modulated together with a pilot signal, a chroma signal and a luminance signal and then recorded on a magnetic tape.
When the thus recorded signals are reproduced from the magnetic tape, it is determined by comparing the average level of the vertical blanking periods of the reproduced AFM signal (RF signal) with the average level of the AFM signal of one field period whether the AFM signal is the bilingual signal or the stereo audio signal. If it is determined that the AFM signal is the bilingual signal on the basis of the detected result, then the bilingual signal is not subjected to the addition and subtraction processings. On the other hand, if it is determined that the AFM signal is the stereo audio signal, then the stereo audio signal, i.e., the sum and difference signals of the left and right audio signals are subjected to the addition and subtraction processings to thereby obtain left and right audio signals.
In the above method in which the average level of the AFM signal of the vertical blanking period and the average level of the AFM signal of one field period are compared with each other, if the level of the AFM signal fluctuates, then the level difference between the average level of the AFM signal of the vertical blanking period and the average level of the AFM signal of one field period is decreased. As a consequence, even though the vertical blanking period of the AFM signal is boosted, it is erroneously determined that the AFM signal is the stereo audio signal. Further, even though the vertical blanking period of the AFM signal is not boosted, it is also erroneously determined that the AFM signal is the bilingual signal. There is then the disadvantage that a boosted pilot signal cannot be detected satisfactorily.